In manufacturing of advanced semiconductor devices (both memory and logic) certain integration schemes require a selective removal of a metals (e.g., Cu, CuMn, Ta, TaN, Al, AlCo, Co, CoMo, Ru, RuTa, RuTiN, Mn, TiN (Self-stop), W, Pt) or dielectrics (e.g., silicon oxide, silicon nitride, silicon carbide, polysilicon) or polymers (e.g., PR, SOG type oxide) with cessation of removal upon reaching a barrier layer (commonly referred to as “stop on barrier”). Compositions and methods for chemical mechanical polishing (CMP) of the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries, CMP slurries, and CMP compositions) for CMP of surfaces of semiconductor substrates (e.g., for integrated circuit manufacture) typically contain an abrasive, various additive compounds, and the like. In the case of barrier layers formed from titanium nitride (TiN) and titanium/titanium nitride (Ti/TiN), the stop on barrier process can be difficult, since typical CMP compositions are not particularly selective for removal of the overlying metal layer relative to the TiN or Ti/TiN layer.
One particular application of the stop on barrier technique is in tungsten (W) gate formation, which involves CMP removal of a W layer disposed on a barrier layer over an oxide substrate. A depression in oxide substrate is lined with a portion of the barrier layer and filled with the W metal. During polishing, the W layer is removed by CMP down to a planar portion of the barrier layer. A portion of W within depression then is removed by etching to form a gate structure. One major difficulty in the stop on barrier technique is undesired removal of the planar portion of the barrier layer, which can lead to a lower gate height or other problems. Often, CMP compositions are not selective enough to reliably and consistently stop material removal when the barrier layer is exposed.
In view of the difficulties encountered in metal removal over a TiN or Ti/TiN barrier, there is an ongoing need for CMP compositions and methods that achieve effective metal removal while suppressing Ti/TiN barrier removal. The methods and compositions described herein address this need.